combobox adding new record

[dcollins]

I have a subform whose recordsource is tblIPAddress, which is a table with three fields-assetnum, IPAddress, Hostname. The table is a fixed list of all IP addresses available. I have a combo box on the subform whose control source is the IPaddress field and the rowsource is a "select" which queries the table 'tblIPAddress'. My problem is that when you are adding a new asset and you select an IP address from the combobox on the subform, it creates a new record in the tblIPAddress table. I don't want it to create a new record, I want it to basically assign the new assetnum to the selected IP address. How can I stop it from adding a new record? If I don't use the IPAddress as control source of the combobox then when you scroll through the records on the main form it doesn't display the IPaddress if one has been assigned. Unless there is another way to do this. I hope this makes sense, it seems so simple but I have struggled with it for days. Any ideas would be appreciated. Thanks.